Fluorescent illumination



June 17, 1947. o. w. ABERNATH-Y ,4

FLUORESCENT ILLUMINATION I Filed Jul 24. 1944 ON-OFE I LINE Patented June 17, 1947 FLUORESCENT ILLUMINATION David W. Abernathy, Chicago, IllQassignor; by

mesne assignments, to Helene Curtis Industries, Inc., a corporation of Illinois Application July 24, 1944, Serial No. 546,294

3 Claims. (Cl. 315282) This invention relates to improvements in fluorescent illumination and more particularly concerns a new and improved method ofhand means for adapting a fluorescent light source' -for such uses as in photocopy work or the like where an intensity of illumination not normally attained with a fluorescent tube is requisite.

A prime consideration in photocopy work and especially for color reproduction, is the requirement for illumination of adequate intensity .and color value to assure an accurate, clear, and sharp image of the subject upon the film or plate of the camera, with as nearly as possible true color separation. A real problem has been encountered, however, in satisfactorily attaining a proper combinatlon of intensity of illumination and color value of the light. Carbon arc lights proved unsatisfactory due to the intense heat developed, and other limitations inherent in this form of illumination. Subsequently it was proposed to employ incandescent lamps in a bank of such 2 special fllters must be employed tion, thus increasing the necessary exposure time and slowing the photocopy process.

. important object of the present invention is following:

characteristic freedom from operating heat inherent in fluorescent lighting.

To provide a photography lamp which can be used with a low or ordinary luminous output for number as to develop the necessary light. Such I expedient is undesirably expensive, heavy, and cumbersome and also develops terrific heat and consumes a heavy load of current, as high as 400 to 500 watts in a typical unit.

Certain advantages in emciency and lower current consumption are obtained in a later, widely used adaptation of the Cooper-Hewitt lamp employing a mercury vapor tube. Nevertheless, the Cooper-Hewitt lamp arrangement is encumbered with certain inherent deficiencies and objectionable characteristics. Among these may be mentioned a rather high current consumption, a unit comparable to a 4.00 or 500 watt incandescent unit using approximately 375 watts. A very cumbersome, heavy, expensive. and heat producing transformer arrangement is an essential part of the unit. There is also considerable weight in the unit as a result of the mercury in the lamp. The Cooper-Hewitt lamp is extremely critical as to position, failing to operate unless the lighting tube is disposed within critical angular limits to accommodate the mercury. Moreover the mercury vapor tube is unduly sensitive to abuse and preliminary or preparatory purposes and also with a high or greatly intensified light output for actual photographing.

To providea light weight lamp unit of this character.

To provide a newand improved portable photocopy lamp unit which is relatively small, compact and of simple construction, which will occupy a minimum of floor space and can be easily and quickly moved about as required.

To provide a photocopy type of lamp unit which is substantially universally adjustable with respect to the subject to be illuminated.

To provide illumination, for photocopy purposes, of such quality as to attain superior color separation without the use of special color filters (except for unusual effects) and thereby save all of the additional exposure time heretofore required where filters have been necessary.

To provide a photocopy type of illumination source which is of unusually low initial .cost and which will operate more economically than comparable prior light sources. I

To provide a photocopy light source which is quite durable and relatively insensitive to abuse.

Other objects,features, and advantages of my invention will be apparent from the following description and the accompanying one sheet of drawings, in which:

Figure 1 is a wiring diagram embodying features of the invention.

Fig. 2 is a perspective view of a photocopy type of lamp unit embodying the features of the invention.

for color correctaken substantially along the line 3-3 of Fig. 2.-

Flg. 4 is an elevational view of the lamp unit showing the head in a vertical position rather than horizontal as in Fig. 2.

Having reference to the exemplary wiring diagram in Fig. 1, a fluorescent lighting tube i6 is shown as deriving electrical current from an alternating current source through a line, indicated by the general numeral ii, and electrical leads i2 and 13 connected to the filaments at the respectlve opposite ends of the tube. As illustrated,

' the circuit is of such character that the fluorescent tube In may be of a standard variety readily available on the market, consisting of an elongated glass cylinder or envelop internally coated with a fluorescent material selected to emit light of the preferred quality. In brief, the internal coating of the envelope is adapted to fiuoresce with a prescribed result when excited by a mercury ,vapor arc struck between the thermionic flla ments located within the respective opposite ends of the tube.

. A conventional starting circuit It connects the filaments of the tube ill and has an automatically operating starting switch it therein. This starting circuit I4 operates in a well known manner to short circuit the path of are between the filaments for a sufiicient length of time after closing of a main circuit on-ofl switch I! to provide for heating of the filaments as the result of resistance to passage of electrical energy through the filaments while the starting circuit is closed. Coincident with attainment of proper thermionic temperature of the filaments, the starting switch i5 opens, whereupon the lighting arc is struck be tween the filaments and the starting circuit I4 is cut out of further operation during maintenance of the arc. I

As is customary in fluorescent lighting circuits, the principal circuit i2, I3 is provided with acurrent-controlling ballast I8. This is connected into one of the leads of the principal circuit, herein the lead. l3 and preferably comprises an autotransformer l9 and a choke coil 20, connectedin series. Thus, when the line switch I! is closed, a circuit is completed from one side of the line through the lead I2 and from the otherside'oi' the line through the lead l3 with the auto-transformer l9 stepping up the voltage slightly and the choke coil 20 supplying the required inductive voltage increase for starting the fluorescent tube I when the starting switch l snaps open. After the lighting arc has been struck through the fluorescent tube ill, the choke coil 20 operates, of course, as a filter to dampen possible fluctuations in the current.

Up to this point has been described merely an ordinary fluorescent lighting circuit wherein the fluorescent tube In is started with a momentarily multiplied voltage within permissible safe limits for which the fluorescent tube has been rated. In this way the fluorescent tube is saved from any unusual load or surge of current at the start which might have any tendency to cause premature deterioration of the filaments. Thereafter the running voltage with the circuit as thus for described will be that prescribed for the particular fluorescent tube being employed. .For example, for a 100 watt tube the circuit voltage may ignited. In this I take advantage of the overrating customarily built into these tubes, that is the potentially greate brilliance of which they are capable'than the standard brilliance when run at the prescribed rate. To this end, I increase the amperage of th current impressed across the fluorescent tube H3 at least to the extent which will eflect up to the saturation point of lumens output of the fluorescent coating of the tube. Within the usual internal or coated surface area limits of a standard watt white light tube this may mean as high 'as 50% increase over normal in the intensity of illumination. If desired, of course, the fluorescent tube may be of greater than normal internal fluorescing area so as to attain greater stepped up brilliance. than with the standard size. While through my method of securing increased illumination the life of the fluorescent tube is considerably shortened in comparison with its normal life expectancy if run at normal pressure, this is tolerable and really no -loss when considering the very desirable results i been ignited through the medium of the starting circuit l4 and the initial ballast l8, as heretofore described, the multiplying circuit switch 23 is closed. This cuts in the multiplying circuit 22 and to a controlled extent increases the flow of current to the fluorescent tube III. For this purpose the supplemental ballast 2| has, in a typical installation in practice, been an identical counterpart of the initial ballast l8, and has comprised an auto-transformer 2d and a choke coil 25. However, the supplementary current input into the fluorescent tube It can be selectively varied within certain limits by appropriate selection of v the effective supplementary ballast elements such as the auto-transformer 24 and the choke coil 25.

In the aforementioned typical installation where the fluorescent tube llldrew a normal running current of approximately .87 ampere, the cutting in of the multiplying circuit 22 caused the delivery of a current of approximately 1.5 amperes through the circuit.

The supplementary circuit switch 23 may be referred to for convenience as a high-low switch because when it is open the fluorescent tube In is operating on low current or input and when the switch is closed the tube operates on high input. Stated in other words, when the high-low switch 23 is open, thetube It] operates at low or normal luminosity on current passed by the initial ballast l8 while when the switch is closed the tube is characterized by its greatly in- 1 creased brilliance or high luminosity as a result of the additional current passed by the supplemental ballast 2|.

An important industrial application of my invention is in a lamp unit for photocopy work, an exemplary practical form of which is shown in Figs. 2, 3, and 4. This lamp is portable, of relatively light weight so that it can be easily shifted around as required, and practically universally adjustable with respect to the subject to be copied or photographed. It comprises a reflector hood 21 removably supporting the elongated fluorescent tube l and'is carried adjacent to one end substantially cantilever fashion by an adjustment head 28 disposed at the top of a vertically adjustable standard 29 mounted upon a preferably caster-equipped portable base 30. By preference, the fluorescent tube II] should be of the largest size commercially available so as to attain maxi-' mum illumination value through the use ofa single tube in the lamp; thus adding compactness to the other attributes of the lamp. The largest presently available fluorescent tube is rated at 100 watts, about 4,000 lumens, and is about60 inches long. The reflector hood Zl is therefore of ample length to receive the fluorescent tube In between appropriate terminal supports 3| and is of such calculated radius and internal construction as to afford the best practicable concentration of light for the intended purpose. Reflected angular surface arrangement behind the tube,

parallel and substantially co-extensive therewith within the reflector hood and in the present instance comprising a member 32 having deflecting surfaces converging on the diameter of the tube substantially as shown in Fig. 3. The deflector 32 also provides a convenient channel or conduit for supportin electrical wiring for the fluorescent tube circuit. Substantial universality of adjustment relative to the subject to be photographed is attained for the reflector 21 through the particular manner of mounting employed. To this end the supporting head 28 is formed of a bracket 33 attached to the hood 2'! and comprising in the main a fixed cylindrical swivel 'shaft 34 whiclris engaged by a releasable clamp 35 secured to a head body 31 by means of a rotary locking member 38 having a conveniently manipulatable hand wheel head. The clamp 35 can be loosened enough to adjust the reflector hood2'l to any desired incremental position through an arc of 180 degrees about the axis of the shaft 34. 'Several such positions of adjustments being indicated in Fig. 3 in full and broken outline.

Swinging adjustment of the reflector hood 21 vertically through 90 degrees from a horizontal position as shown in Fig. 2 to a vertical position as shown in Fig. 4 is accomplished by having the clamp 35 mounted rotatably on the axis of the hand wheel locking member 38 and under the control of the locking member. Moreover, light can be thrown from rather high up because due to the substantially eccentric or cantilever mounting of the deflector 21 it extends to a considerable height when tilted up on end. Also as a result of this eccentricity the reflector can be adjusted freely over a wide area to one side of the supporting stand and standard.

To enable elevational adjustment of the reflector 2'3, the standard 29 is preferably constructed of telescopic members which may comprise an outer tube 39 fixed in upright position to the base 30, and an inner telescopic member 40 fixed to the head body 3? and vertically slidable within the outer tube 39 throughout a substantial range of vertical adjustment. Any preferred condition of relative vertical adjustment of the standard elements 39 and M1 is adapted to be maintained through the medium of internal looking or sustaining structure or mechanism (not shown) of any preferred form under manual control of means such as a manually operable knob or button 4| conveniently disposed on the head body 31. By preference the inner telescoping member 40 of the standard is rotatable at will within the outer member 39 so.that the lamp reflector may be swung about the standard axis as needed.

Inasmuch as the ballasts l8 and 2i are of relatively small size andcompact they are preferably arranged in-elongated form and mounted directly upon the reflector hood 2l enclosed within an elongated cover lzlwhich may be removably secured longitudinally upon the back of the hood 2'1. For purpose of stability the ballast assembly is preferably located so that its center of mass is as close as practicable to the axis of the standard 29. Connection with an electricalsource outlet is adapted to be convenientlyeffected through the medium of a plug 03 carried by an electrical cable or cord M.

For the convenience and guidance of the'user, the switches H and 23 are located in readily 'ac-' cessible well separated positions on the lamp unit and are appropriatelyidentified. .In a preferred arrangement the switches are assembled with the ballast structure adjacent to the respective opposite ends of the cover 42 as seen in Fig. 2 and have suitable switch-operating levers projecting from the cover. Proper legends identifying the line switch IT by On-off" or the like and the auxiliary circuit switch by such wording as High-low are preferably provided on the cover 42 adjacent to .the respective switch operators.

From the foregoing it will be apparent that I have provided a lamp construction which is unique in several respects. Although the method and means whereby the increased luminosity of the fluorescent tube is attained has many obvious useful applications, the outstanding results obtained in the photocopy field demand special attention. In a unit comparable in luminosity to a Cooper-Hewitt unit rated at about 375 watts, a

commercially available watt fluorescent tube will give entirely satisfactory results when stepped up to about to 200 watts. Instead of a, heavy, cumbersome and profusely heat emitting transformer arrangement as requiredv for operation of a Cooper-Hewitt lamp, the present lamp is adapted to be equipped with but a small, compact relatively light weight ballast unit which can be conveniently mounted directly on the reflector hood. The amount, of heat generated by the ballast and the fluorescent lamp i quite insignificantso that where the lamp is used in relatively confined quarters as in a photographic studio or a'photocopy work shop-a much higher I degree of comfort may prevail with respect to temperature than has prevailed with prior expedients. The small compact form of the lamp hood and its practically universal adjustment are of great advantage to the user, since the illumination source can thus be maneuvered with great freedom into precisely the position with respect to the subject under illumination deemed most with normal intensity light and without the glaring brilliance which is necessarily incident to the maximum illumination developed by the lamp for actual photographing after the supplementary ballast circuit is closed by throwing the highlow switch to high position. After the subject has been photographed, the lamp need not be shut ofl entirely but merely by opening the highlow switch 23the illumination can be cut back to normal until photographing illumination is again called for. The life of thfluorescent tube is thus extended rather than shortened as would be the case were it to be shut ofi altogether and then restarted over and over again during a working period.

While I have illustrated and described a. certain preferred embodiment of my invention, it is to be understood that I do not thereby intend to limit my invention to the specific details disclosed, but contemplate that various modificationjs, substitutions, and alternative constructions may be effected without departing from the spirit and scope of the-invention as defined in the appended claims.

I claim:

1. A fluorescent lighting circuit comprising a fluorescent lamp, a choke coil and auto transformer connected in series with said lamp, starter means, and means for increasing the intensity of illumination of said lamp, said. means comprising a choke coil and auto transformer connected in series with each other but both connected in .parallel with said first mentioned coil and transformer, and aswitch for selectively connecting said last mentioned coil and transformer into said circuit. a

2. A fluorescent lightingcircuit comprising, in combination, a fluorescent lamp, starter means connected across the terminals thereof, a current ballast including a choke coil and auto transformer connected in series with said lamp, and means for increasing the intensity of illumination of said lamp, said means including an auxiliary ballast comprising a series of connected choke coil and auto transformer connected in parallel with said first mentioned ballast, and switching means for selectively connecting said auxiliary ballast into said circuit.

3. A fluorescent lighting circuit comprising, in combination, a fluorescent lamp, starter means connected across the terminals thereof, a current ballast including a choke coil and auto transformer connected in series with said lamp, means for multiplying the current input into said lamp to increase the lumens output thereof, said means comprising a choke coil and auto transformer connected in series with each other but both connected in parallel with said first mentioned current ballast, and switching means for selectively connecting said last mentioned coil and transformer into said circuit.

DAVID w. ABERNATHY. REFERENCES orrEn The following references are of recordinthe file of this patent:

UNITED STATES PATENTS Number Name Date 2,392,845 Foerste Jan. 15, 1946 1,930,123 Ewest Oct. 10, 1933 2,298,935 Freeman Oct. 13, 1942 1,994,305 Dorgelo Mar. 12, 1935 2,114,842 Inman Apr. 19, 1938 2,018,254 Dobrusskin Oct. 22, 1935 2,178,423 Inman 0ct. 31, 1939 1,744,370 Dietz et a1. Jan. 21, .1930

. 2,286,851 Hess June 16, 1942 2,297,781 Korengold Oct. 6, 1942 2,332,770 Abernathy Oct. 26, 1943 2,258,354 Doane Oct. 7, 1941-, 1,291,945 Libson Jan. 21, 1919 D. 136,799 Vendope Dec. 7, 1943 FOREIGN PATENTS Number Country Date 386,552 Great Britain c 1933 OTHER REFERENCES Chanon & Barr, Some engineering aspects of 4 

